Is there a way to round corners on material level?
A straightforward solution has been added to the most recent Blender distributions (after the released version of 2.79b, so you must download newer updates of 2.79b, or 2.80 Alpha, from https://builder.blender.org/download/ to enable it).

There's a single node (Input&nbsp;>&nbsp;Bevel) that fakes bevelled normals. Of course it won't change the geometry, so it doesn't look great from too close, but it can enhance pretty convincingly the specular/reflection at the edges.